1. Technical Field of the Invention
The present invention relates to a method of processing cross sections of samples using a focused ion beam for, for example, observing cross sections of a semiconductor devices or manufacturing samples for TEM (transmission electron microscope), and a method of manufacturing cross section observation samples.
2. Description of the Related Art
Samples having micropatterns such as semiconductor devices or semiconductor laser devices are increasingly miniaturized. Therefore, cross section processing is generally performed with FIB (focused ion beam) when observing the cross sections of the samples with an SEM (scanning electron microscope) or when slicing these samples into thin sections for fabricating samples for TEM (transmission electron microscope).
When the cross section processing is performed on a sample having projections and depressions on a surface thereof, there is a problem such that the etching speed by the FIB is fluctuated because of the influence of the projections and depressions, so that vertical lines are formed on a cross-sectional surface. Therefore, as a technique to form a film on the surface of the sample by CVD (chemical vapor deposition) induced by the FIB before performing the cross section processing is known (JP-A-2-152155).
In contrast, in recent years, in the semiconductor processing for example, there is a demand for performing the cross section processing of the samples having a resist pattern on the surfaces thereof or the fabrication of the TEM sample with the FIB in order to confirm whether the resist patterns are formed with high degree of accuracy.
However, when an attempt is made to perform a processing of the cross section of the sample on which an organic substance such as a resist film or the like on the surface thereof with the FIB, there arises a problem such that the fragile organic substance becomes damaged by the FIB, and hence the shape or the structure is changed (deformed), so that sufficient observation of the cross section cannot be achieved. Even when a protective film is formed by the FIB induced CVD before the cross section processing as described in JP-A-2-152155, the organic substance becomes damaged by the FIB emitted in this procedure. In contrast, even when the protective film is formed on the sample before the cross section processing by an electron beam, the organic substance on the sample is deformed.